A Gentle Introduction to Category Theory: the calculational approach by Maarten M. Fokkinga
1994
Number of pages: 80
In these notes we present the important notions from category theory. The intention is to provide a fairly good skill in manipulating with those concepts formally. This text differs from most other introductions to category theory in the calculational style of the proofs, the restriction to applications within algorithmics, and the omission of many additional concepts and facts that I consider not helpful in a first introduction to category theory.
Mathematics Category Theory